Accurate climate reconstruction from fossil corals: The impact of seawater carbonate chemistry on the Sr/Ca, d18O and d11B of coral aragonite

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The chemistry of tropical coral skeletons reflects the seawater temperature and chemistry at the time the coral lived and the analysis of fossil coral skeletons offers an excellent route to reconstruct high resolution (~monthly) climate records. These high resolution records are essential for understanding past changes in global climate e.g. for studying the frequency and severity of El Nino in the past, and for testing global climate models for predicting 21st century climate change.However, despite this potential, it is clear that other factors also affect the chemistry of coral skeletons and these influences need to be resolved if the climate information recorded in fossil skeletons is to be accurately interpreted. In this research we will investigate if past changes in seawater pH affect the chemistry of coral skeletons. Seawater pH was probably higher in the recent past (over the last 500,000 years), reflecting lower atmospheric CO2 levels. We will culture corals over a range of seawater pH and determine how pH affects skeletal chemistry. We will develop a methodology to correct for past variations in seawater pH, allowing us to reconstruct accurately past seawater temperatures from the chemistry of fossil skeletons.